The station first signed on as KFIV-FM on July 4, 1977, with a Top 40 format.[4] This was the station that was "portrayed" in the George Lucas film American Graffiti, where Wolfman Jack was supposedly broadcasting from. It was a very popular station in Modesto and was part of youth culture there, until its change to an adult contemporary format in late 1988. In 1989, the station became its present KJSN.